Constant hum, sudden silence or intermittent noise - This is how the average user most often notices the operation of the cooling system. For many owners of household appliances, it is a revelation that modern models fan do not spin around the clock. Understanding the cyclical nature of its operation is necessary in order to distinguish normal operation from an incipient breakdown that requires the intervention of a technician.
In systems No Frost i Total No Frost air circulation is the basis for maintaining a given temperature. If the motor-compressor creates cold, then it is the fan that carries it through the chambers. However, if you hear that the device has been working continuously for several hours, or, conversely, is silent when the compressor is on, this is a reason to conduct a detailed diagnosis of the condition of the unit.
In this article we will analyze the physical principles of the evaporator, standard time intervals for various brands and algorithms by which the electronic control module makes a decision about starting or stopping the impeller. You will learn to determine when a humming sound is normal, and when it signals critical icing or a malfunction of the electric motor.
The principle of operation of the air circulation system
The fundamental difference between refrigerators with an automatic defrosting system is forced convection. Unlike static cooling, where the cold falls down by gravity, here air flow it is directed by channels specially designed for this. A fan located behind the back wall of the freezer draws in warm air, drives it through the frozen evaporator and returns it back to the chamber already cooled.
It is important to understand that the operation of this unit is tightly synchronized with compressor. In most models, the fan starts almost simultaneously with the start of the motor-compressor, but with a slight delay of a few seconds. This is necessary so that the refrigerant begins to circulate through the evaporator tubes, and the air is not wasted through the warm radiator.
However, there are nuances in the operating algorithms of different manufacturers. For example, in some models Liebherr or Siemens the fan can continue to run for another 5-10 minutes after the compressor stops. This is done to more effectively use the accumulated cold and equalize the temperature in different corners of the chamber before completely shutting down the system.
⚠️ Attention: If you hear the fan operating, but the compressor is silent and does not vibrate at this moment, this may indicate sticking relay contacts or an error in the temperature sensor, which “thinks” that the compressor is working.
Air circulation also serves to prevent the formation of large ice crystals on food. The constant movement of dry cold air prevents moisture from settling on the chamber walls and packaging. That is why in such refrigerators the products air out faster if they are not covered with a lid, and require the use of containers.
Standard operating cycles and duration
The answer to the question “how long the fan should work” does not have one universal number in minutes, since the duration of the cycle directly depends on the heat flow into the chamber. If you have just loaded a package of warm food or often open the door, cooling cycle it will take longer. In normal mode, when the refrigerator is in operation, the operation of the fan usually coincides with the operating time of the compressor.
The average operating cycle of a modern refrigerator is from 15 to 30 minutes, followed by a pause of a similar or longer duration. Thus, the fan spins approximately 50% of the time of the total cycle. However, when first turned on or after defrosting, the unit can work non-stop for up to 12 hours until it reaches temperature.
There is also the concept of a “small cycle”, which is characteristic of inverter compressors. In such systems, the fan may not stop completely, but only reduce rotation speed (revolutions), switching to economy mode. This creates the illusion of constant operation, but the noise level is minimal and energy consumption is reduced.
Below is a table showing the approximate ratio of the operating time of the compressor and fan in various situations:
| Situation | Compressor status | Fan status | Cycle duration |
|---|---|---|---|
| Normal mode | Working | Working | 15-30 min |
| Waiting | Disabled | Disabled | 20-40 min |
| Defrosting | Disabled | Disabled | 20-30 min |
| First power-on | Working | Working | Up to 12 hours |
Relationship with defrost cycle
One of the most important points that often frightens users is the complete stop of the fan during the defrost cycle. In refrigerators No Frost on the evaporator, frost inevitably forms from the moisture contained in the food. Approximately once every 8-12 hours (or according to sensor data), the system goes into defrost mode defrost.
At this moment, the compressor and fan are forcibly turned off by the electronic module. It turns on Defrost heating element, which melts the ice on the radiator. If the fan continued to work at this moment, it would simply blow warm air from the heater throughout the freezer, which would lead to spoilage of food and overload of the system.
The duration of the pause in the fan operation during defrosting is usually from 15 to 30 minutes. After the defrost sensor detects water draining or reaching a certain temperature, the heating element turns off. The fan will not start immediately - the system waits until the compressor starts pumping refrigerant again so as not to drive warm air.
Why does the fan start with a delay after defrosting?
The delay is necessary to stabilize the pressure in the system and begin cooling the evaporator tubes. If you start the blowing immediately, warm air will enter the chamber in the first seconds, which will disrupt the temperature regime.
If you notice that after a long silence (defrost cycle) the fan does not start when the compressor starts, this is an alarming symptom. Perhaps it froze in an ice coat or its electric motor failed, which requires immediate inspection, since without airflow the evaporator will quickly become covered with ice and stop cooling.
Reasons for continuous fan operation
The situation when the fan hums for hours without a break, even when the compressor, it would seem, should be resting, indicates a violation of heat exchange. Most often, the reason lies in loose door fit. If the seal (elastic band) is damaged or a foreign object gets on its edge, warm, moist air constantly enters the chamber.
The control system detects the increase in temperature and commands the compressor and fan to work without stopping, trying to compensate for the heat inflow. In this case cyclicity it is broken, and the unit works for wear. Check the cleanliness of the seal and the tightness of the door closure.
Another common reason is clogging of the air exhaust channels or too dense loading of the chambers with products. If you block the cold air outlets, the temperature sensor may not detect cooling. As a result, the fan continues to spin, trying to blow air through obstacles, but the effectiveness of this process is zero.
⚠️ Attention: Continuous operation of the fan for more than 2-3 hours in standby mode (without loading new products) can lead to overheating of the motor winding and its subsequent combustion.
It is also worth checking the temperature settings. If you set the temperature to the lowest possible temperature (for example, -24°C or Super Freeze mode), the refrigerator will operate almost without interruption. In the summer, when the ambient temperature in the kitchen is high, this gets worse, and pauses in operation may disappear completely.
Diagnostics of noise and extraneous sounds
Normal operation of the fan is accompanied by a smooth, monotonous hum. However, users often encounter changes in the nature of the sound. Squeaking, crackling, or whistling noises indicate mechanical problems. Most often, engine bushings wear out, which requires lubrication or replacement of the unit. bearings engine bushings, which requires lubrication or replacement of the unit.
The impeller itself can produce an extraneous sound. If it is unbalanced or ice is frozen on its blades, beating occurs. Vibration is transmitted to the body and amplified by resonance. Sometimes the cause of the crackling sound is wiring that has sagged too close to the blades and periodically touches them during rotation.
For diagnostics, you can carefully remove the plastic panel of the back wall in the freezer (after unplugging the refrigerator from the mains!). A visual inspection will reveal ice on the blades or foreign objects. If the fan turns with difficulty by hand or makes a grinding noise, its resource is exhausted.
☑️ Checking the source of noise
Some models, for example, the brand Indesit or Atlant, use a fan with an asymmetrical mount. When replacing it, it is important not to confuse the orientation, otherwise even a serviceable part will create increased noise and vibration due to mass imbalance.
The influence of ambient temperature
External conditions play a huge role in the duration of operation of the blowing system. In winter, when the kitchen is cool, the refrigerator turns on less often and the fan cycles become shorter. In the summer, especially in the heat above +30°C, heat exchange is disrupted, and the unit is forced to work almost continuously.
The critical point is to install the refrigerator close to the wall or in a niche without gaps. For normal operation of the condenser (grid at the back) and effective heat exchange, air flow is necessary. If the refrigerator overheats outside, its internal system also works with overload, increasing the fan rotation time.
There is a concept of climate class of equipment. If a device designed for a temperate climate (SN, N) is installed in an unconditioned room in the southern sun, its automation may not cope. The fan will work constantly, but the temperature in the chamber will still be higher than the set one.
What to do if the fan does not stop
If you are sure that the door is closed tightly, the food does not block the ducts, and the temperature in the room is normal, but the fan hums for hours, you need to check the serviceability of the sensors. The main suspect is defrost sensor or the evaporator temperature sensor. If it “lies” and shows that there is not enough cold, the control module will keep the fan on.
The second possible reason is a freon leak. If there is a lack of refrigerant, the system cannot gain temperature, the compressor runs non-stop, and the fan follows suit. In this case, no settings will help; you need to call a technician to find a leak and refuel.
It is also worth checking the serviceability of the electronic control module itself. A burnt-out relay can “stick” in a closed state, constantly supplying power to the fan, even if the operating logic of the device requires it to be turned off. This is diagnosed by continuity of the relay contacts when the power is turned off.
Why does the fan turn on with a characteristic click?
The click before the fan starts or stops is the sound of the electromagnetic relay on the control board operating. The relay physically opens or closes contacts, supplying 220V to the motor. If there is a click, but the fan is silent, the problem is in the fan motor or an open circuit.
Is it possible to turn off the fan manually?
Technically, you can break the power circuit, but this is strictly forbidden during operation. Without air circulation in the No Frost system, the evaporator will be covered with ice in a few hours, after which the cold will stop flowing into the chamber, and the food will spoil.
Does the fan hum in refrigerators with a drip system?
In classic refrigerators with a “crying” evaporator (only in the refrigerator compartment), there is usually no fan. There the cold spreads through natural convection. The fan can only be there if it is a Full No Frost model, where both the freezer and the refrigerator compartment are blown by force.
How often do you need to change the fan?
The service life of modern electric fan motors is designed for 7-10 years of continuous operation. However, due to moisture, icing and power surges, they may fail earlier. Scheduled replacement is not required, only in the event of a breakdown or strong noise.
Does the operation of the fan affect energy consumption?
Yes, but only slightly. The consumption of the fan motor itself is only 5-10 watts. The main energy consumer is the compressor. However, if the fan is faulty and does not cool the evaporator effectively, the compressor will work longer, which will ultimately increase the overall electricity bill.